Device and method for treating a filtration medium

ABSTRACT

A device for processing a porous filtration medium has a holding part that can be mounted on a lower part with the porous filtration medium. An outer wall of the holding part can be positioned outside a surface, of the filtration medium, and a fixing edge arranged in the holding part can be positioned on an edge of the filtration medium. The holding part has a filtration support which, on its side facing away from the filtration medium, is connected to an outlet for reverse flushing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a device for processing a porous filtrationmedium, having a holding part which can be mounted on a lower part,wherein an outer wall of the holding part can be positioned outside asurface, which can be used for filtration, of the filtration medium, anda fixing edge which is arranged in the holding part can be positioned onan edge of the filtration medium.

The invention also relates to a method for processing a porousfiltration medium, in which method a holding part of a device is mountedon the filtration medium which is arranged in a lower part of afiltration device and which is exposed to a liquid sample, wherein afixing edge which is arranged in the holding part is connected to anedge of the filtration medium and is raised, together with thefiltration medium connected thereto, from the lower part.

2. Description of the Related Art

In the field of the analysis of liquids and gases, various processingmethods have become established which use porous media such as filtersand diaphragms. For example, the filtration method has becomeestablished for the depletion and concentration of dissolved orparticulate components. Said concentration is usually necessary becausethe concentrations of the impurities are too low to carry out directevaluations. The filtration methods serve as a preliminary stage forfurther analytical methods, such as optical evaluations, and also forfurther physical and chemical reactions for signal enhancement.

For newer, more sensitive analysis methods such as PCR (“PolymeraseChain Reaction”) or mass spectrometry analysis, only very small samplevolumes can be used. To be able to filter the in many cases typicalsample volumes of more than 100 ml for the purpose of concentration, useis typically made of filtration diaphragms of 47 mm or 25 mm diameter.Even after the filtration, when the components or particles are presentin concentrated form on the filtration diaphragm, the particles bound tothe diaphragm cannot be supplied directly for analysis owing to thediaphragm size. It is necessary to transfer the retained components intoa sample volume. If the sensitivity of the methods is to be fullyutilized, said volumes must be as small as possible. Volumes of lessthan 1 ml, preferably 100 μl to 1 μl, are desirable, because, forexample for PCR analysis, use is typically made of volumes of 20 μl to 1μl, and the corresponding unused sample residual quantities come at theexpense of sensitivity.

DE 10 2008 005 968 A1 discloses a nutrient medium unit and a method forreceiving a filter from a filtration device. Here, the nutrient mediumunit is composed of a cover or a holding part, which forms the actualtransfer unit, and of a lower part which is filled with nutrient medium.Here, the upper part, which is formed as a holding part, has a fixingedge which, for the removal of the filtration medium from the filtrationor processing device, can be connected to an edge of the filter by meansof an adhesive bond.

DE 10 2008 005 968 A1 furthermore discloses a method for themicrobiological examination of liquid samples, in which a cover or aholding part of a nutrient medium unit is mounted by way of a fixingedge on a filter which is arranged in a lower part of a filter orprocessing device and which is formed as a diaphragm filter. Here, thefixing edge of the holding part is connected to an edge of the filter bymeans of an adhesion layer.

The holding part is subsequently raised together with the filter from afilter support of the lower part of the filter device, and placed on asurface of a nutrient medium arranged in a lower part of a nutrientmedium unit, wherein the cover or the holding part covers theshell-shaped lower part.

A disadvantage of the known filtration units and of the correspondingmethods which have proven themselves for classic microbiologicaldiaphragm applications, and which involve merely the removal ofparticles or, in the field of microbiology, the visual evaluation ofcolonies which have formed, is however that, after the filtration, theretained particles or the components thereof can no longer be removedfrom the diaphragm by flushing in such a way as to form highlyconcentrated suspensions.

Said disadvantages are of significance in particular in applicationswhich do not correspond to the classic growth of retained germs on agar,but which rather use the modern molecular-biological marking anddetection methods, regardless of whether these methods requirepre-incubation or are examined directly by marking or enhancementmethods.

DE 20 2004 005 694 U1 discloses an apparatus system for liquid testing,which apparatus system has, on a frame, a suction connecting piece towhich is fastened, via an adapter, a filter bracket with a filtrationdiaphragm or a filtration medium, wherein a removable funnel is situatedon the filter bracket. After a filtration process, the funnel isremoved, and a DNA binding column is inserted, for further testing,between the suction connecting piece and adapter.

It is a disadvantage here that it is not possible for a universalfiltration device or processing device to be used. It is also adisadvantage that, during the individual manipulations, there is therisk of contamination. It is also a disadvantage that reverse flushingof the filtration medium is not possible.

EP 1 566 209 A1 discloses a device and a method for vacuum-assistedaffinity chromatography.

Here, too, a special device is required in which, furthermore, differentexchangeable parts yield the risk of cross-contamination. In saiddevice, too, as in the other devices, reversible flushing is not easilypossible without removing the filtration medium.

It is therefore an object of the present invention to provide a deviceand a method with which it is possible for a porous filtration medium tobe inserted in a simple and cheap manner, without further technicalaids, into a further processing station in which, by means of thereverse filtration of a very small quantity of liquid, a large amount ofthe retained components can be transferred, in highly concentrated form,into a small volume.

SUMMARY OF THE INVENTION

The object with regard to the device is achieved in that the holdingpart has a filtration support which, on its side facing away from thefiltration medium, is connected to an outlet for reverse flushing.

It is preferable here for that side of the filtration support whichfaces toward the filtration medium to face toward the retentate side ofthe filtration medium.

As a result of the arrangement of a filtration support in the holdingpart above the filtration medium, which filtration support is connectedto an outlet, it is possible for the device or the holding part to beinserted upside down into a further processing station and for reverseflushing to be carried out without the filtration medium having to beremoved from the holding part. The filtration medium is preferablydisk-shaped and may be a porous diaphragm or some other suitable filter.

The device may form a separate filtration device or may be at least partof a separate filtration device. Here, the lower part and the holdingpart may be formed as disposable articles. It is also possible for thedevice as a whole to be formed as a disposable article or formed fromdisposable articles.

The lower part may however also be part of a first filtration devicefrom which, with the holding part, the filtration medium is removed.

In one preferred embodiment of the invention, a detachable collectingvessel is connected to the outlet of the holding part. Since the outletis already connected to a collecting vessel, the particulate componentscan be flushed out of the filtration medium and collected directly inthe collecting vessel, without the need for an additional manipulationwith the risk of contamination.

In a further preferred embodiment of the invention, the fixing edge ofthe holding part can be connected to the edge of the filtration mediumby means of an adhesive bond. Here, the fixing edge of the holding partor the edge of the filtration medium has an adhesion layer composed of asuitable adhesive. By means of the adhesion layer, the disk-shapedfiltration medium adheres to the holding part and can be easily removedfrom the processing device and processed further. It is howeverbasically also possible for the fixing edge of the holding part to beconnected to the edge of the filtration medium by means of a clampingconnection.

The disk-shaped filtration medium which is coordinated with theprocessing device provided is usually of rotationally symmetricaldesign, though may also have a rectangular structure or some otherpolygonal structure and also geometrically irregular forms. Thecorresponding device for holding a filtration medium or the holding partis functionally coordinated, in terms of its encircling contour, withthe contour or structure of the disk-shaped filtration medium so as toproduce adhesive contact or a clamping connection only in the regionwhich has not been wetted by the medium and the preceding filtration,and which is not used for further analysis.

The adhesion layer is formed from a PSA (“Pressure Sensitive Adhesive”)dispersion adhesive or from acrylate copolymer microspheres. In thisway, even wet filters can be adequately bonded to the fixing edge of theholding part and if appropriate also removed again. Suitablepressure-sensitive adhesives are known to a person skilled in the artfor example as acrylate adhesives based on microspheres. Here, adhesivesmay be used which can be sterilized using common methods.

Furthermore, adhesives are used which do not exhibit any non-specificreactions or signals with reagents and reaction methods used in thesubsequent analytics. In particular, the adhesive is preferably freefrom DNA and protein and has no elutable components which, by staining,fluorescence or chemical reaction, disrupt the subsequent analytics.

In a further preferred embodiment of the invention, a cover whichcorresponds to the holding part can be mounted on the holding part withfiltration medium held therein, wherein the cover has a cavity which isformed as a reservoir and distributor for flushing liquid. In this way,the holding part can be used as a liquid distributor which serves forthe contacting, for the dosing of the spatial distribution and for theuniform discharging of the flushing liquid during the contacting andflushing process. Here, the holding part is formed such that, after theremoval of the porous filtration medium with the holding part from afirst processing device, said holding part is mounted and fixed on thetop side or retentate side of the filtration medium. Here, the cover canclose off the underside of the filtration medium such that a reversecontamination of the filtration medium and of the sample volumes duringthe handling steps is prevented.

In a further preferred embodiment of the invention, the cover has, onthe side facing away from the holding part, an orifice which can berepeatedly reclosed by a closure. Different quantities and/or types offlushing or processing liquids can be introduced through the orifice.

In a further preferred embodiment, the cover has further orificesarranged and formed so as to ensure uniform, air-bubble-free filling ofthe flushing liquid reservoir.

In a further preferred embodiment of the invention, the reservoir isfilled with a porous medium. The porous medium serves to absorb anddistribute the flushing liquid over the filtration medium. The porousmedium of the reservoir may bear areally against the underside of thefiltration medium. The cover is formed with its reservoir such that itcan absorb and areally distribute a defined volume.

The holding part and the associated cover may be designed such that thefiltration medium is sealed off radially toward the edge in the regionoutside the filtration surface by the cover, and such that outflow ductsand surfaces are provided which are situated below the filtration mediumand which are angled so as to slope downward toward the collectingvessel. By means of these and other similar sealing features, it can beensured that, in the case of centrifugation flushing, all of theflushing medium is conveyed through the filtration medium into thecollecting vessel, without remaining in the region laterally outside thefiltration medium owing to the centrifugal force, and thus being lostwith regard to the further analysis.

The cover may be sterilely packaged and in particular delivered in astate in which it is sterilely closed off at its underside, which facestoward the holding part, by means of a detachable sterile barrier. It isalso possible for the cover to be delivered in a state in which it isfilled with flushing liquid. Here, the flushing liquid is particularlysuitable for releasing adherent particles during the reverse flushing.In particular, the flushing or processing liquid is suitable forreleasing the microorganisms adhered to the filtration medium, lysingsaid microorganisms and/or extracting the components then released.

As a result of the contact of the cover which is filled with processingliquid, it is possible, by means of a corresponding time and temperatureprofile, to ensure that corresponding reactions with the adherent germsare completed before the reaction products are transferred, by thereverse flushing, into the collecting vessel or into adjoining filteringor adsorption units.

The holding part and the cover are suitable for the correspondingsubsequent analytics, and are in particular free from disruptivecontaminants. For PCR in particular, DNA-free products are required.

In a further preferred embodiment of the invention, between the outletof the holding part and the collecting vessel, there are fitted aremovable filter and/or a corresponding adsorption unit which permitfurther processing steps for concentration, purification and elution.

The object with regard to the method is achieved in conjunction with thepreamble of Claim 11 in that the holding part with the filtration mediumheld therein is turned upside down, and that components retained on thefiltration medium are reverse-flushed out and collected in a detachablyconnected collecting vessel.

As a result of the fact that the holding part with the filtration mediumheld therein is turned upside down, it is not necessary for thefiltration medium to be removed from the holding part for the purpose ofreverse flushing. The collecting vessel which is connected to theholding part furthermore reliably prevents the possibility of undesiredcontamination during the mounting of the collecting vessel. The outlayfor reverse flushing is thus made considerably simpler and safer.

The device for the processing of the filtration medium may be deliveredin sterilely packaged form. Here, the holding part may be closed off atits holding opening, which is arranged on the underside facing away fromthe outlet, by a sterile closure for example in the form of an adherentfoil. The sterile closure projects with a tab laterally beyond thecircumference of the holding part.

Before the first use of the device or of the holding part, the sterileclosure is gripped by the tab and pulled off the holding part.

In a preferred embodiment of the invention, after the holding part isturned over, a cover having a cavity which forms a reservoir and whichhas been filled with flushing liquid is mounted onto the holding partand inserted into a further processing device, wherein the liquid isdischarged from the reservoir in order to flush out the components.

As a result of the fact that the cover is mounted onto the holding partafter the latter is turned over, the holding part with the filtrationmedium and the cover can be inserted into a further processing station,for example a centrifuge, in a simple and safe manner. Withoutadditional manipulation, it is possible for the filtration medium to bereverse-flushed with liquid from the reservoir, or centrifuged, in theprocessing station, such that the retained, preferably particulatecomponents are flushed out and collected by the collecting vessel of theholding part.

The cover may likewise be delivered in sterilely packaged form. Inparticular, the free space, which is formed as a flushing liquiddistributor, of the cover may likewise be provided so as to be sterilelyclosed off in the direction of the holding part by a detachable sterilebarrier. The sterile barrier may for example be in the form of anadherent foil.

The sterile barrier projects with a tab laterally beyond thecircumference of the cover.

Before the first use of the cover, the sterile barrier is gripped by thetab and pulled off the cover.

Simple and cheap manipulation of the filtration medium with the sampledeposited thereon is thus attained.

Further features of the invention will emerge from the followingdetailed description and from the appended drawings, which illustratepreferred embodiments of the invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side view of a device for processing a filtration mediumin section, having a holding part with a filtration support, having anoutlet with a collecting vessel plugged thereon, and having a sterileclosure.

FIG. 2 shows a sectional side view of a first filtration device with afiltration medium arranged on a lower part.

FIG. 3 shows a sectional side view of the holding part from FIG. 1 onthe lower part with filtration medium from FIG. 2.

FIG. 4 shows a sectional side view of the holding part of FIG. 1, withfiltration medium and mounted cover, turned upside down.

FIG. 5 shows a sectional side view of the cover of FIG. 4 with a sterilebarrier.

FIG. 6 shows a sectional side view of a further holding part withfiltration medium and mounted cover.

FIG. 7 shows a sectional side view of a further device for processing afiltration medium, composed of a holding part with a filtration support,of an outlet with collecting vessel plugged thereon, and of a sterileclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A device 1 is composed substantially of a holding part 2, of afiltration support 3 and of an outlet 4.

The holding part 2 forms an encircling contour with an outer wall 5 andwith an inner wall 6 running parallel thereto, said inner wallsurrounding a shoulder 7 in the holding part 2, which shoulder isdelimited in the upward vertical direction by a top wall 8 which has, inthe cylindrical outlet 4 integrally formed thereon, a central orifice 9.The filtration support 3, which is composed of a material permeable toliquid, is arranged in the shoulder 7.

The holding part 2 has, on its holding part inner surface 10 facing awayfrom the top wall 8, the inner wall 6 whose free end forms, with its endsurface, a fixing edge 11. In the exemplary embodiments, the fixing edge11 has an adhesion layer 12 composed of a suitable adhesive.

The adhesion layer 12 is formed for example from a PSA dispersionadhesive or from acrylate copolymer microspheres.

A collecting vessel 14 is plugged onto the lateral surface 13 of theoutlet 4. The collecting vessel 14 which is detachably connected to theoutlet 4 is formed for example as an Eppendorf vessel known per se or“spin tube”.

Corresponding to the exemplary embodiment of FIG. 1, the holding part 2has, on its free end of the outer wall 5, a sealing sterile closure 15which can be pulled off the holding part 2 or the outer wall 5 by meansof a tab 16.

A first processing device known per se, which is formed, correspondinglyto FIG. 2, as a filtration device 17, is composed of a lower part 18with a holding shoulder 19 onto which a funnel-shaped attachment 20 canbe mounted. Between the attachment 20 and a filter support surface 21 ofthe lower part 18 there is arranged a preferably disk-shaped filtrationmedium 22 formed for example as a porous filter diaphragm.

After a filtration process, the attachment 20 can be removed from thelower part 18, and the holding part 2 of the device 1 can, with thecollecting vessel 14 plugged thereon, be mounted on the lower part 18 inplace of the attachment 20. Here, the holding part 2 is mounted with itsfixing edge 11 onto an edge 23 of the disk-shaped filtration medium 22,such that the disk-shaped filtration medium 22 adheres to the adhesivelayer 12 of the fixing edge 11 and can be held by the lower part 18 asper FIG. 3.

The device 1 or the holding part 2 can now, with the filtration medium22, be turned upside down as per FIG. 4, wherein the disk-shaped porousfiltration medium 22 rests on the underside 24, which faces away fromthe top wall 8, of the filtration support.

A cover 25 can be mounted, as per FIG. 4, onto the inner wall 6 of theholding part 2 with the filtration medium 22 in order to close off thedevice 1 or the holding part 2.

The cover 25 comprises a cavity 26 which serves as a reservoir anddistributor for flushing liquid. The cavity 26 is filled with a porousmedium 27 which can store flushing liquid and which serves as adistributor.

The dimensions of the cover 25 are such that it, by means of its innersurface 34 of the side wall 35, laterally encompasses the fixing edge 11of the holding part 2 at the lateral surface 33 of the inner wall 6, andit comes to rest on the filtration medium 22.

The cover 25 has, on its outer side 28 facing away from the holding part2, a central orifice 29 for flushing stages, which orifice can be closedoff by a closure 30. The orifice 29 permits uniform, areal wetting andaeration of the reservoir or cavity 26 in the porous medium 27 thereof,which can be easily saturated with flushing liquid and which alsouniformly discharges said flushing liquid again during the flushingprocess, for example by centrifugation.

For the flushing process, a pressure compensation device, for example anair orifice, must be provided between the collecting vessel 14 and theoutlet 4, and between the closure 30 and the cover 25, in order to beable to correspondingly effect the liquid changes.

The flushing process may be carried out under the action of differentdriving forces, for example by vacuum filtration after the opening ofthe closure 30 and the sealing mounting of the holding part 2.

Centrifugation is preferable because, by means thereof, it is possiblefor extremely small volumes to be collected in the collecting vessel 14.

The cover 25 with the cavity 26 formed as a flushing liquid reservoirmay also be offered in sterile form with a sterile barrier 31 includingopening tab 32 in order to prevent contamination of the sample.

FIG. 6 illustrates a device 1′ whose holding part 2′ with the filtrationsupport 3′ is designed especially for a centrifugation application. Theholding part 2′ forms an encircling contour with an outer wall 5′ whichsurrounds a shoulder 7′ in the holding part 2′, which shoulder isdelimited in the upward vertical direction by a top wall 8′ which has,in the cylindrical outlet 4′ integrally formed thereon, a centralorifice 9′. The filtration support 3′, which is composed of a materialpermeable to liquid, is arranged in the shoulder 7′.

The holding part 2′ has, on its holding part inner surface 10′ facingaway from the top wall 8′, a circular fixing edge 11′ which surroundsthe filtration support 3′. In the exemplary embodiments, the fixing edge11, 11′ has an adhesion layer 12 composed of a suitable adhesive. Thetop wall 8′ is formed such that its inner outflow surface 36 is offrustoconical form, sloping downward at an angle φ with respect to ahorizontal toward the collecting vessel 14.

A cover 25′ can be mounted into the holding part 2′ with the filtrationmedium 22 in order to close off the device 1′ or the holding part 2′, asper FIG. 7.

The cover 25′ comprises a cavity 26′ which serves as a reservoir anddistributor for flushing liquid. The cavity 26′ is filled with a porousmedium 27 which can store flushing liquid and which serves as adistributor.

The dimensions of the cover 25′ are such that it completely covers thefixing edge 11′ of the holding part 2′ and the filtration medium 22′,comes to rest on the filtration medium 22′ and fills out the interior ofthe holding part 2′.

The cover 25′ has, on its outer side 28′ facing away from the holdingpart 2′, a central orifice 29′ for flushing stages, which orifice can beclosed off by a closure 30′. The orifice 29′ permits uniform, arealwetting and aeration of the reservoir or cavity 26′ in the porous medium27 thereof, which can be easily saturated with flushing liquid and whichalso uniformly discharges said flushing liquid again during the flushingprocess, for example by centrifugation.

In the inner surface 37 of the outer wall 5′ there is arranged anencircling annular depression 38 which corresponds to a bead 39 on thecover 25′. The cover 25′ is thereby fixed. The filtration medium 22 issealed off radially to the outside by means of a sealing edge 40 of thecover 25′, in that the sealing edge 40 presses into the filtrationmedium 22 as per FIG. 7.

By means of these and other similar sealing features, it is ensuredthat, in the case of centrifugation flushing, all of the flushing mediumis conveyed through the filtration medium 22′ into the collectingvessel, without remaining in the region laterally outside the filtrationmedium 22′ owing to the centrifugal force, and thus being lost withregard to the further analysis.

1. A device (1, 1′) for processing a porous filtration medium (22, 22′),the device comprising a holding part (2, 2′) that can be mounted on alower part (18) with the porous filtration medium (22, 22′), an outerwall (5, 5′) of the holding part (2, 2′) being positionable outside asurface, that can be used for filtration of the filtration medium (22,22′), and a fixing edge (11, 11′) arranged in the holding part (2, 2′)and being positionable on an edge (23) of the filtration medium (22,22′), the holding part (2, 2′) having a filtration support (3) which, onits side facing away from the filtration medium (22, 22′), is connectedto an outlet (4) for reverse flushing.
 2. The device of claim 1, whereinthe lower part (18) is part of a first filtration device (17) fromwhich, the holding part (2) and the filtration medium (22) can beremoved.
 3. The device of claim 1, wherein a detachable collectingvessel (14) is connected to the outlet (4).
 4. The device of claim 1,wherein the fixing edge (11, 11′) of the holding part (2, 2′) can beconnected to the edge (23) of the filtration medium (22, 22′) by anadhesive bond.
 5. The device of claim 1, wherein the fixing edge (11,11′) of the holding part (2) can be connected to the edge (23) of thefiltration medium (22, 22′) by a clamping connection.
 6. The device ofclaim 1, claim 1, wherein the fixing edge (11, 11′) of the holding part(2, 2′) or the edge (23) of the filtration medium (22, 22′) has anadhesion layer (12) composed of a suitable adhesive.
 7. The device ofclaim 1, wherein a cover (25, 25′) that corresponds to the holding part(2, 2′) can be mounted on the holding part (2, 2′) with filtrationmedium (22, 22′), and in that the cover (25, 25′) has a cavity (26, 26′)formed as a reservoir and distributor for flushing liquid.
 8. The deviceof claim 7, wherein the cover (25, 25′) has, on its side facing awayfrom the holding part (2, 2′), an orifice (29) that can be closed off bya closure (30).
 9. The device of claim 1, wherein, between the outlet(4, 4′) and the collecting vessel (14), there are fitted a removablefilter and a corresponding adsorption unit which permit furtherprocessing steps for concentration, purification and elution.
 10. Thedevice of claim 1, wherein the lower part (18) and the holding part (2,2′) are disposable articles.
 11. A method for processing a porousfiltration medium (22, 22′), comprising mounting a holding part (2, 2′)of a device (1, 1′) on the filtration medium (22) that is arranged in alower part (18) of a filtration device (17) and which is exposed to aliquid sample, connecting a fixing edge (11, 11′) arranged in theholding part (2, 2′) to an edge (23) of the filtration medium (22, 22′)and raising the holding part, together with the filtration medium (22,22′) connected thereto, from lower part (18), turning the holding part(2, 2′) with the filtration medium (22, 22′) held therein upside down,and reverse flushing-out and collecting components retained on thefiltration medium (22, 22′) in a detachably connected collecting vessel(14).
 12. The method of claim 11, wherein, after the holding part (2,2′) is turned over, a cover (25, 25′) having a cavity (26, 26′) thatforms a reservoir and that has been filled with flushing liquid ismounted onto the holding part (2, 2′) and is inserted into a furtherprocessing device, wherein the liquid is discharged from the cavity (26,26′) in order to flush out the components.